Another difference between SRW and DRW is how the wheels mount. If you have messed with duallies you already know this. Dually wheels are hub-centric, meaning they rely on a very precise fit at the hub to determine the centering and bearing of the wheel when mounted. The lug nuts are not tapered into the rim (the rims are flat on both sides). Chevy has used a ring between nuts and wheels while Ford uses flat washered nuts.
SRW trucks have a fairly good fit at the hub, but the lugs are tapered into the rims, helping to positively locate.
Be very careful when getting spacers. I ordered a set of aluminum spacers for my '85 K30 dually from somebody out west, and they were just flat disks with holes to mount to existing lugs and lugs to mount the outer rim. There was nothing to center the rim! Too much play in lug holes. I can't remember the company, but my friend's F350 had steel spacers with a ring sticking out to catch the outer rim. Very strong. Chevy's have a different hub diameter and the only way to make those spacers work for me would have been to use Ford outer rims.
But that old K30 was a gasser so I sold it and now I'm burning oil!
Norm<br />1995 K3500 Crew Cab SRW/Util.Body<br />L65 6.5TD, 4L80E, 4.10, LT265/75R16E, K+N air filter/box mods, Firestone Air Bags, JK Fan Clutch/Fan, 3\" exhaust